1. Field of the Invention
The present invention relates to a storage system and method for managing data using the same. In particular, the invention relates to a storage system having an improved journaling file system, and a data backup and restoration method employing the journaling file system.
2. Description of Related Art
In order to protect data from accidental loss in computer systems, data is backed up, and restored/recovered using storage apparatuses. Snapshot technology and journaling technology are well known for data protection technologies used in a computer system. The snapshot technology includes storing data images (snapshot data) for a file system or volume at a point in time. For example, if data has been lost due to a failure, the data can be restored to its state prior to the data loss, by referring to the stored snapshot data. The journaling technology includes storing, upon data-write, the data to be written and the timestamp of the data-write, as journal data. In recent years, storage apparatuses provided with high-speed data restoration mechanisms integrating those journaling and snapshot technologies have been receiving attention.
As one example, Japanese Patent Laid-open Publication No. 2005-18738 discloses a storage apparatus that, in response to a write request from a host apparatus, stores journal data for application data to be stored in a data volume and also stores snapshot data for the data volume, for example, at regular intervals. If restoration of data as of a particular point in time is requested, the snapshot data closest to the requested point is applied to a data volume, and then the relevant journal data is applied, restoring data in a final state.
In conventional manners of restoring data, system administrators generally select a particular past point to which data is to be restored, which is called a restore point or recovery point, and have a data volume restored as it is at the selected restore point in the past. While at work, the system administrator usually attempts data restoration not only for just one restore point, but for several restore points so that optimum restoration results can be obtained.
According to the conventional manners, the above-explained steps need to be executed every time data restoration is attempted for each new restore point. More specifically, even if one restore point is just changed to another, the same series of steps, including application of snapshot data and application of journal data, needs to be performed. Those steps put a large load on the system, and so a considerable length of time is taken for restoration, but even so, no efficient method for data restoration has been considered until now.